The present invention relates to an escapement arranged between a gear train and a plate to which is attached a balance of a timekeeper, the balance being able to travel through a free arc of oscillation and to receive pulses for maintaining the oscillations, this escapement including first and second toothed wheels meshing with each other, one of such wheels being driven by the gear train.
The Applicant of the present invention has already proposed an escapement answering the definition which has just been given and a description of which is set out in European Patent No. -A-1 041 459. This document discloses an escapement including first and second wheels meshing with each other. One of these wheels is driven by the gear train. First and second plates secured to a common shaft support a sprung-balance. The wheels and the first plate are provided with means allowing said first plate to receive direct pulses delivered alternately by the first and second wheels for the purpose of maintaining the balance oscillations. The second plate is provided with means for driving a locking lever arranged to lock said first and second wheels alternately.
The present invention thus takes up an essential feature of that which is described in the aforecited document, namely two wheels meshing with each other, one of these wheels being driven by the gear train. However, the idea developed in the aforecited document of using two superposed plates, one used to receive direct pulses provided alternately by the first and second wheels, and the other used to lock alternately, via a lever, said first and second wheels, has been abandoned in the present invention for obvious purposes of simplifying the mechanism.
As will be seen in the following description, a single plate supporting the sprung-balance co-operates with a lever which in turn and alternately co-operates with the first and second wheels. It will thus be understood that the entire escapement mechanism is contained in a single plane and that the space requirement of the mechanism in height is halved with respect to the space occupied by the escapement of the aforecited document.
Thus, the escapement of the present invention is characterised in that it further includes a lever able to receive pulses generated alternately by the first and second wheels and to transmit these pulses to the plate to drive it in rotation and to maintain the oscillations of the balance, said lever being arranged to lock said first and second wheels alternately after each impulse transmitted.
It will thus have been understood that the lever of the invention fulfils a dual function: first of all that of transmitting the pulses received alternately from the first and second wheels to the plate and then that of locking said wheels alternately after each impulse.